Process for hydrometallurgical treatment of an indium chloride solution

ABSTRACT

A process for the hydrometallurgical treatment of an indium chloride solution and at least one element selected from the group consisting of tin and antimony comprises the following steps: a) adjustment of the free chloride ion content by addition of alkaline or alkaline earth chloride or a mixture thereof and of their acidity by the addition of hydrochloric acid; b) bringing said indium chloride solution into contact with an organic phase containing dry trialkyl phosphate; c) extraction of said organic phase by bringing the latter into contact with a 0.1 to 3 N hydrochloric acid solution to obtain an indium chloride solution; d) basic extraction using an alkaline metal hydroxyde. Application to extractive metallurgy and recovery of indium and accompanying elements.

The present invention relates to the recovery of indium and possiblerelated elements contained in a solution of chlorides of indium andvarious other elements and particularly tin chloride and antimonychloride; it particularly relates to the separation of tin and antimonyfrom indium.

The development of novel applications for indium, among which may bementioned the compounds III-V, conductive transparent films used indisplays and in photovoltaics and the mixed indium-tin oxides whichallow the greenhouse effect to be trebled, has made the recovery of thiselement particularly attractive, it often being found associated withores of the common non-ferrous metals, particularly blend, chalcopyriteand galena.

The recovery from a sulphate solution has already been the subject ofnumerous studies and patents, particularly the French Patent Applicationpublished under the number 2,435,533.

It happens that in the course of pyrometallurgical processes indiumaccumulates in various phases which may readily be subjected tochlorinated dissolution, with or without oxidation, to give a solutionof indium chloride. Certain solutions of metallic chloride, such asthose which are produced by the process described in the French Patent2,317,366, may contain indium which it may be opportune to recover.

The separation of indium from tin and antimony, elements to which it ischemically similar, is known technically but the solutions which havebeen proposed are not satisfactory and are expensive to use. Inparticular, extractions have been proposed using organic compounds ofthe ether type or of the ketone type; more particularly, numerousstudies have been based on methyl isobutyl ketone.

However, all these products are volatile and present fire risks andexplosion risks which are not negligible.

For this reason one of the objects of the present invention is toprovide a process for the hydrometallurgical treatment of a solution ofindium chloride, which may be mixed with tin chloride or antimonychloride, which uses an extractant which should not be inflammable orexplosive.

Another object of the present invention is a process which allows a goodseparation of indium chloride from antimony chloride and that of tin.

These objects, and others which will appear subsequently, are achievedby means of a process for the hydrometallurgical treatment of a solutionof indium chloride and at least one element selected from the groupcomprising tin and antimony, characterized in that it comprises thefollowing steps:

a) adjustment of the concentration of free chloride ion by addition of achloride of an alkali metal or a chloride of an alkaline earth metal ora mixture of these and adjustment of their acidity by addition ofhydrochloric acid;

b) bringing the said solution of indium chloride into contact with anorganic phase comprising trialkyl phosphate;

c) reextraction of the said organic phase by bringing the latter intocontact with a solution of 0.1 to 3N hydrochloric acid, to obtain asolution of indium chloride;

d) basic reextraction using an alkali metal hydroxide.

The adjustment of the concentration of chloride ion and acidity isimportant because it is desirable to extract essentially all therefinable elements and because the concentration of chloride ion and theacidity have a very great influence on achieving this recovery usingtrialkyl phosphate Preferably, the concentration of free chloride ion isadjusted to a value in the range 3 to 12N and the acidity to a value inthe range 1 to 6N. This adjustment is preferably made using calciumchloride; a particularly advantageous range is a solution of indiumchloride which contains in addition 5 to 10N chloride ions preferably inthe form of calcium chloride and 1 to 3N acidity. Generally theconditions are within the median values of these brackets.

"Free chloride ion" is understood to mean chloride ions which are notassociated with an element whose extraction is desired, using trialkylphosphate, in the form of an uncharged complex (for example InCl₃,HInCl₄ and so on); generally speaking, free chloride ions associatedwith hydrochloric acid or with alkali metals or alkaline earth metalsare considered as free chloride ion. Within the scope of the presentinvention ammonium ions will be counted as alkali metal ions.

With the aim of better controlling the liquid-liquid extraction, bothwith regard to the level of viscosity and to chemical properties, it isdesirable that the trialkyl phosphate should be dissolved in aromatichydrocarbons; generally aromatic hydrocarbons are selected frompetroleum fractions having high boiling points and high ignition points,such as the type sold under the trade name Solvesso 150. Generally, foreconomic reasons, tributyl phosphate is used as the trialkyl phosphate,better known by the abbreviation of its letter symbol in English TBP.

The organic phase preferably contains from 20 to 60%, advantageouslyfrom 30 to 50% of trialkyl phosphate by volume.

One of the objects of the present invention is to recover, with thehighest possible yield, the metal values contained in the chloridesolution while being as selective as possible with regard to impurities.As described above good extraction using trialkyl phosphates can beachieved by controlling the levels of chloride and acid in the solution.As for selectivity, apart from the usual techniques particularly thatconsisting in increasing the number of extraction stages, it is achievedby adjusting the quantity of trialkyl phosphate which is placed incontact with the solution to be extracted, taking account of the factthat the complexes formed between trialkyl phosphate and the chloridecomplex to be extracted require three molecules of phosphate for asingle atom of the element to be extracted, under usual conditions.

Taking into account that tributyl phosphate, subsequently designated bythe letter symbol in English TBP, is the most commonly used and the mosteconomical trialkyl phosphate, TBP will serve in the rest of thedescription as the paradigm of this family.

Thus, the equations for extraction of tin and indium are essentially ofthe type:

    ______________________________________                                        2H.sup.+ + Sn.sup.4+ + 6Cl.sup.- + 3 TBP                                                           H.sub.2 (SnCl.sub.6) - 3 TBP                             H.sup.+ + In.sup.3+ + 4Cl.sup.- + 3 TBP                                                            H(InCl.sub.4) - 3 TBP.                                   ______________________________________                                    

The principal other species extracted are: SnCl₄, 2 TBP; SnHCl₃, 3 TBP;Sn(OH)Cl₃, 3 TBP; InCl₃, 3 TBP; InCl₄, 3 TBP. The associated speciesHCl, TBP and HCl, 2 TBP, are also present.

The reaction with antimony is of the same type and also uses threemolecules of TBP. Thus to calculate the stoichiometry, a value of threemolecules of TBP will be assumed for one atom of the element to beextracted.

Thus, to achieve good selectivity it is advisable to control the ratioorganic phase/aqueous phase (O/A) and the outputs of the differentphases, so that the amount of trialkyl phosphate which is put intocontact with the said solution of indium chloride and the chloride of atleast one element chosen from the group comprising tin and antimonyshould contain at least between 1 and 11/2 times, preferably between 1and 1.2 times, the stoichiometric quantity necessary for the completeextraction of tin, antimony and indium. When iron III is present at asignificant concentration, that is, at a concentration above a value ofthe order of 1 gram per liter, it is advisable to add to thisstoichiometric quantity the stoichiometric quantity necessary to extractiron III, which is solvated by three molecules of TBP.

Generally a value of the order of 10% above the stoichiometric quantityis selected.

The determination of the right proportion within these brackets dependson the temperature, which may vary from ambient temperature to thatallowed by safe use of the selected diluent (60°-70° C.), on the degreeof dilution, the impurities and a compromise between good recovery andgood selectivity.

The intended recovery is preferably greater than 90%, advantageouslygreater than 95%.

This technique gives satisfactory results when the molar ratio of indiumon the one hand, to the sum of antimony and tin on the other hand, isgreater than a seventh, advantageously greater than a fifth. When thisratio is less than the values above, it is desirable to eliminate partof the antimony and tin by an extraction prior to the principalextraction which will be based on indium.

This can be carried out by incorporating a step a') in the process,before step b), in which the said solution of indium chloride and atleast one element selected from the group comprising tin and antimony isplaced into contact with a solution of trialkyl phosphate, the quantityof trialkyl phosphate which is put into contact being less than thestoichiometric quantity necessary for extracting the whole of the tinand antimony, preferably less than 80% of this value. When iron III ispresent at a significant concentration, that is at a concentration abovea value of the order of 1 gram per liter, it is advisable to add to thisstoichiometric quantity the stoichiometric quantity necessary to extractiron III, which is solvated by three molecules of TBP. In any case, thisquantity must be such that the ratio indium/antimony+tin is within thelimits specified above after extraction. In order to avoid changes ofacidity when the phases TBP and the indium-containing solutions to beextracted are placed into contact, it is preferable to place thesephases in prior contact with a solution of approximately 2N hydrochloricacid.

When arsenic is present to a significant extent in indium-containingsolutions it is preferable to adjust the redox potential of the saidsolution in such a way that the ratio arsenic V/total arsenic is atleast equal to 90%, preferably to 95%. Indeed, it is one of theteachings of the present invention, that under the conditions ofextraction described in the present application, arsenic V is much lesseffectively extracted than arsenic III.

The reextraction step c) has a very important influence in achieving areextraction solution which is lean in tin, antimony and, ifappropriate, in iron and other coextracted elements. This step must becarried out in such a way that the final total concentration of chlorideions after reextraction is at least equal to 2N, preferably is in therange 3 to 8N, generally in the region of 5-6N. This final concentrationof chloride ions can be controlled either by adjusting the concentrationof hydrochloric acid initially present in the reextraction solution, orby adjusting the O/A ratio and adjusting the concentration of indium inthe organic phase. It should be noted that, for the purposes ofadjusting the concentration of indium in the organic phase the priorextraction step a') has a large effect on the concentration of indium inthe organic phase. The solution of indium chloride obtained afterreextraction in step c) from the organic phase can be subjected to anextraction by an uncharged organic TBP phase, the O/A ratio beingcontrolled in such a way that there are 2 to 5 times the stoichiometricquantity necessary to extract the whole of the tin which is present inthis indium chloride solution.

The following examples, while not presenting any limitingcharacteristic, are intended to enable specialists to determine easilythe operating conditions which it is advisable to use in each particularcase.

EXAMPLE 1

A solution of PHA_(inf) is placed in contact with an organic phasecontaining 40% of TBP and 60% of SOLVESSO 150 (by volume), so as toachieve a ratio of organic phase to aqueous phase of 0.8, in acountercurrent manner within a battery of 5 mixer-settlers. Havingreached chemical equilibrium within the battery, an organic phasePHO_(eff1) is obtained whose composition, as well as that of PHA_(eff1),is given below.

In a second step, the organic phase PHO_(eff1) loaded with tin, indiumand antimony is placed in contact with an aqueous phase titratingHCl=2N, so as to obtain a ratio O/A=8, under countercurrent conditionswithin a battery of 4 mixer-settlers. The indium is thus completelyreextracted from the organic phase and after reaching chemicalequilibrium within the battery, an organic phase PHO₂ is obtained and anaqueous reextraction phase PHA_(eff2) concentrated in indium, therespective compositions of which are given in the table below.

In a third step, the organic phase PHO_(eff2) loaded with tin andantimony is placed in contact with an aqueous phase titrating NaOH-4.5N, so as to obtain a ratio O/A=1.5, in a countercurrent mannerwithin a stirred reaction vessel. The antimony and tin are thuscompletely reextracted and a three-phase mixture is obtained which,after filtration and decanting, gives an organic phase no longercontaining any metallic element and recyclable by extraction, an aqueousphase containing sodium PHA_(eff3) rich in tin and a solid cake ofsodium antimonate. The composition of PHA_(eff3) is given in the tablebelow.

    __________________________________________________________________________    Chemical                                                                            PHASES                                                                  species                                                                             PHA.sub.inf                                                                       PHA.sub.eff1                                                                       PHO.sub.eff1                                                                        PHA.sub.eff2                                                                       PHO.sub.eff2                                                                        PHA.sub.eff3                                  __________________________________________________________________________    Sn (g/l)                                                                            25  0.02 31.2  12   29.7  44.6                                          In (g/l)                                                                            7   0.02 8.7   70   0     0                                             Sb (g/l)                                                                            2   0.004                                                                              2.5   3    2.1   0.007                                         Pb (g/l)                                                                            21.4                                                                              21.4 0.002 0.001                                                                              0.002                                               Cu (g/l)                                                                            22.0                                                                              22.0 0.002 0.016                                                                              0.002                                               Zn (g/l)                                                                            2.0 2.0  0.034 0.3  0.002                                               CaCl.sub.2 (M)                                                                      3   3                                                                   H.sup.+ (M)                                                                         2   2          3.5                                                      OH.sup.- (M)                    2.5                                           __________________________________________________________________________

It can be seen from the table above that the molar ratio in PHA_(inf) ofindium to tin plus antimony is less than 0.5, that the degree ofrecovery after extraction is greater than 99%, that the selectivity ofthe extraction of tin, antimony and indium is largely complete inrelation to other extractable elements such as copper and zinc and thatthe enrichment factor of indium in the re-extraction phase PHA_(eff2) isgreater than 20 in relation to tin and greater than 70 in relation toantimony.

EXAMPLE 2

Prior Purging of Tin, Antimony and Iron

The object of the present example is to show the possibility of aselective separation of tin, antimony and iron from indium using the TBPmixture.

A solution whose composition is shown below and titrating HCl 2N andCaCl₂ 3M is placed in contact with a TBP-SOLVESSO mixture (40-60% byvolume equivalent to 1.4M), under counterflow conditions, within abattery of mixer-settlers in two stages. The ratio O/A is selected insuch a way that the quantity of TBP used is that whichstoichiometrically fixes the whole of the antimony and iron as well as80% of the tin. In the present case the ratio O/A is 0.55.

The results are compiled in the table below.

    ______________________________________                                        Elements (g/l)   Sb     Sn       In  Fe                                       ______________________________________                                        Stock solution   3.1    28.5     6.4 0.48                                     Depleted solution                                                                              0.1    4.4      6.3 0.05                                     Loaded solvent   5.4    43.8     0.5 0.87                                     Yield from extraction (%)                                                                      97     84       1.3 100                                      ______________________________________                                    

The possibility of extracting virtually the whole of the iron andantimony and 84% of the tin without significant extraction of indium isthus confirmed.

EXAMPLE 3

Purification of the Reextraction Solution

The object is to eliminate the tin contained in an acid solution ofindium chloride which results from step c) of the process.

During the trial, the aqueous solution is placed in contact with anorganic phase TBP 40% SOLVESSO 150 60% under countercurrent conditionsin a battery of mixer-settlers in three stages. The ratio O/A iscalculated so as to extract virtually the whole of the tin withoutentraining too much indium. In the present case the ratio O/A is 0.33.

The results are compiled in the table below.

    ______________________________________                                        Elements (g/l)   Sn         In     Sb                                         ______________________________________                                        Stock solution   10         70     1.2                                        Depleted solution                                                                              0.1        68.7   0.35                                       Loaded solvent   30         3.9    2.6                                        Yield from extraction (%)                                                                      99         2      71                                         ______________________________________                                    

The possibility of removing tin from a solution of indium chloride isconfirmed. At the same time a large part of the contained antimony iseliminated.

The solvent which is thus loaded with tin can be recycled to step b).

We claim:
 1. Process for the hydrometallurgical treatment of a solutionof indium chloride and at least one element selected from the groupconsisting of tin and antimony, comprising the following steps:a)adjusting the concentration of free chloride ion in said solution to avalue within the range of 3 to 12N by addition of a chloride selectedthe group consisting of a chloride of an alkali metal, a chloride of analkaline earth metal and a mixture of these, and adjusting the acidityof said solution to a value in the range 1 to 6N; b) separating theindium and the at least one element from the adjusted solution obtainedin step a) by bringing said adjusted solution into contact with anorganic phase comprising trialkyl phosphate, so as to obtain an organicphase containing the indium and the at least one element; c) extractingthe indium from the organic phase obtained in step b) by bringing saidorganic phase into contact with a solution of 0.1 to 3N hydrochloricacid so as to obtain a solution of indium chloride; d) extracting the atleast one element from the organic phase obtained in step c) by bringinginto contact said organic phase with an alkaline sodium solutioncomprising an alkali metal hydroxide.
 2. Process according to claim 1,wherein the chloride of step a) is calcium chloride.
 3. Processaccording to claim 1, characterized in that the organic phase is asolution of 20 to 60% by volume of trialkyl phosphate dissolved in anaromatic hydrocarbon.
 4. Process according to claim 3, characterized inthat the said aromatic hydrocarbon is a petroleum fraction.
 5. Processaccording to claim 1, characterized in that during step a) the chlorideconcentration is adjusted to a value within the range 3 to 12N and theacidity to a value in the range 1 to 6N.
 6. Process according to claim1, characterized in that the ratio organic phase/aqueous phase and theoutputs of the various phases are controlled in such a way that thequantity of trialkyl phosphate placed in contact with the said solutionof indium chloride and the chloride of at least one element selectedfrom the group consisting initially of tin and antimony is in the rangeof 1 to 11/2 times the stoichiometric quantity necessary for thecomplete extraction of tin, antimony and indium.
 7. Process according toclaim 6, characterized in that the said quantity of trialkyl phosphateis in the range of 1 to 1.2 times the stoichiometric quantity necessaryfor the complete extraction of tin, antimony and indium.
 8. Processaccording to claim 1, wherein when the molar ratio of indium to the atleast one element is lower than a seventh, the process of claim 1further comprises a step a'), before step b), in which said adjustedsolution of indium chloride and the chloride of the at least one elementselected from the group consisting of tin and antimony is placed incontact with a solution of trialkyl phosphate, the quantity of trialkylphosphate which is placed in contact being less than the stoichiometricquantity necessary for the extraction of the whole of the at least oneelement.
 9. Process according to claim 1, characterized in that prior tostep b) the said organic phase is placed in contact with a 2N solutionof hydrochloric acid.
 10. Process according to claim 1, wherein whensaid solution further consists of arsenic, the redox potential of thesaid solution of indium chloride and the chloride of the at least oneelement is controlled in a way such that the ratio arsenic V/totalarsenic is at least equal to 90%.
 11. Process according to claim 10,characterized in that the redox potential of the said solution of indiumchloride and the chloride of the at least one element is controlled insuch a way that the ratio arsenic V/total arsenic is at least equal to95%.
 12. The process of claim 1, wherein when the molar ratio of indiumto the at least one element is lower than a fifth, the process of claim1 further comprises a step a'), prior to step b), in which said adjustedsolution is placed in contact with a solution of trialkyl phosphate, thequantity of said trialkyl phosphate is less than the stoichiometricquantity necessary for the extraction of the whole of the at least oneelement.